Need help to identify Audio Output issue
Need help to identify Audio Output issue
- Subject: Need help to identify Audio Output issue
- From: Marc Van Olmen <email@hidden>
- Date: Mon, 12 May 2008 23:28:55 -0400
hi,
I need some help trying to identify what is causing this issue.
We are using Decklink video card and we use the QuickTime vOut(video
frames) and uses coreAudio to play out the audio to the device.
Our application has been running fine for a couple of years on several
clients configurations running 24/7. But we have problem that is
coming up for different users:
The audio seems to be later then the video after a long time
(sometimes 24 hours sometimes even quicker).
I recorded a video that records both the the audio video that comes
out the decklink card:
http://www.sky4studios.com/desync/desync.mov
In this sample the delay is 12 frames (25 fps) so about 1/2 second.
But we think that there is something wrong with coreAudio or with the
audio driver of the Decklink drive. Why?
When we pause our application, the audio doesn't stop for 12 frames
(exactly the duration of the desync).
We stop the audio by the following technique: as soon the pause action
is received we start sending 0.0 samples towards the audio output.
When there is no desync of the application this works instantly. But
when there is a desync of audio and video, the audio takes longer to
stop(duration of desync)
Also when we press the continue button, the video frames starts right
away but the audio doesn't starts playing for again exactly the
duration of the desync.
In the video above you can see the Pause/Continue button in action. If
you analyze this clip in Final Cut Pro you see what I'm talking about.
I would love some feedback to figure out if I can proof if this is the
Decklink Driver or is it a coreAudio problem. Is there something I can
turn on in coreAudio when I hear a desync that helps me to proof my
case?
Thanks for any help!!!!
marc
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